In a seat configuration where a seat portion and a seat back portion are structured to be able to integrally adjust a position of the seat portion and the seat back in a forward and backward direction of a vehicle, longitudinal length of a cushion portion in the forward and backward direction of the vehicle is designed based on femoral length of human body. The femoral length of human body varies from individual to individual. However, the longitudinal length of the cushion portion is usually designed to fit with the relatively short femoral length. When the longitudinal length of the cushion portion is designed to fit with the relatively short femoral length, an occupant who has the relatively long femoral length is not able to attain satisfactory comfort to sit in a seat, because the backs of the occupant's knees stick out from the cushion portion in a forward direction.
In a configuration where a cushion portion is movable in a forward and backward direction of a vehicle relative to a frame portion of a seat portion, the cushion portion is movable in the forward and backward direction of the vehicle relative to a seat back portion. Thus, an occupant who has the relatively long femoral length is able to attain satisfactory comfort by moving a position of the cushion portion forward in a longitudinal direction relative to the seat back portion to place a front end side of the cushion portion under the backs of the occupant's knees.
In order to enable the cushion portion to move in the forward and backward direction of the vehicle relative to the frame portion of the seat portion, for example, a bush is interposed between the frame portion and the cushion portion as disclosed in German Patent 10113153 and German Patent 19624979. In the seat which is disclosed in German Patent 10113153, a moving member positioned in a cushion portion side is suspended to a securing member via the bush. The bush is inserted into a longitudinally elongated guide hole provided at the moving member. An elastic portion is provided at the bush. The elastic portion is used for avoiding a clearance between upper and lower guide walls of a guide hole and the bush, and the presence of the elastic portion allows the seat to restrict rattling between the moving member and the securing member.
In the seat disclosed in German Patent 19624979, a moving member positioned in a cushion portion side is suspended to a securing member via the bush. The bush is inserted into a longitudinally elongated guide hole provided at the moving member. An elastic portion is provided at the bush. The elastic portion restricts the rattling between the moving member and the securing member.
However, in German Patent 10113153 and German Patent 19624979, the bush is made of a single material. In order to provide the elastic portion at the bush which is made of a single material, for example, the entire portion of the bush is needed to be made of a resin. In that case, the resin may be severely degraded due to a load caused by weight of the occupant sitting on the seat and age-related degradation. When the degradation of the resin progresses seriously, the rattling occurs between the moving member and the securing member to lose the comfort to sit in the seat.
The present invention has been made in view of the above circumstances, and provides a vehicle seat improving comfort to sit in the seat by preventing the rattling between the cushion portion and the frame portion which movably supports the cushion portion in a forward and backward direction.